1. Technical Field
The present invention relates generally to methods and apparatus for controlled or regulated charging, discharging, or combined charging and discharging of power sources, such as batteries, and more particularly to where an internal such power source charges or operates an external second power source.
2. Background Art
In some manner, we have had electrical power stations nearly as long as we have had electrical power sources. Of present interest are electrical power stations that followed the addition of electrical starting and other electrical accessories in motor vehicles. Such power stations typically have had to meet the electrical requirements of their end application as well as be nominally portable to often be transported to such applications. For instance, a common application is to start an automobile where the owner has left the headlights on depleted the vehicle's battery. A power station suitable for this application must provide 12 volt direct current at sufficient amperes to operate the starter of the vehicle (typically while the vehicle's battery is still connected and presents an additional load as it recharges). Such a power station also usually must be portable to wherever a vehicle's owner parked when they left the headlights, typically a parking lot at their place of employment or at a store or restaurant.
The simplest power station for such an application is another vehicle that has a powerful enough battery, and a set of jumper cables. This simple solution, however, is not one that automotive and other service professionals are comfortable with. For example, a small service vehicle used to service large trucks in the field may not inherently come with or even be fit able with a large enough battery. Moreover, even when this can be done it is inefficient, in the small service vehicle when it is used for other tasks, and it is risky. Batteries become “weak” over time and use, and an aged or heavily used battery that starts a small service vehicle may embarrassingly not still be strong enough in a service application.
Most service professionals tend to prefer stand alone power stations. Historically, continuing mostly with automotive service scenarios but obviously extendable to aviation, nautical, and many other applications as well, a service profession would build or buy a power station with a large battery in an at least semi-portable housing, the a set of heavy cables terminated with suitable clams. In auto service stations one will frequently see such a power station today. It usually has two wheels, to permit easy limited movement, and it can be lifted into a service vehicle for field service calls.
Our society has increasingly come to rely on electrical power, and especially direct current power. Let us consider a few examples. Automobiles are now ubiquitous in some places, but so are cellular telephones and laptop computers. In fact many of us routinely use chargers for these devices that attach to a 12 volt DC power source in our automobiles. Many emergency and other specialty radios today can additionally be or are exclusively are powered with 12 VDC. Some televisions, small air compressors, lighting systems, and heating systems similarly can use 12 VDC. Ironically, an increasingly common electronic device today is power inverters, to convert 12 VDC to 120 or 240 volts, 60 cycle alternating current (AC) power.
Increasingly, people who are not service professionals, as well as ones who are but who want an appliance for personal use, are interested in power stations. These prospective new users want more than an expensive and awkward to handle box. They are willing to compromise on power to get economy, portability, and safety. Unlike service professionals, users here typically need a solution that can be stored between infrequent uses, that can be reliable when needed, and that is safe and easy. Thus, unlike professional service scenarios where lead technology batteries with their attendant their flammable hydrogen fumes, corrosive sulfuric acid, and expensive and environmentally threatening disadvantages may be manageable, a potential user here prefers a non lead-based power source or at least a very reliably sealed and storage-life optimized lead-based power source.
Moreover, these users typically have specific applications in mind and they want a power station that as flexibly as possible fulfills those applications as well as others that they may later encounter. These prospective new users often want sophistication in a power station. Many would like an air compressor and/or a power inverter integrated into a power station, but commercial offerings of such are not common.
Often unappreciated until needed, many such users (as well as many service professionals) would like a power station that provides lighting. There are only two basic ways hook two power sources, such as an automobile battery and a power station. When one cannot see what they are doing they will get it wrong 50% of the time, with great risk to safety and equipment. Service professionals appreciate this an strive to get it right, by also have a separate light source and using it (e.g., having an assistant hold a flash light, even if they have to wait for or go ask an assistant to do this). Lay users are not always so prepared in advance, or so patient, or will have read a power station's safety and usage instructions.
Accordingly, there is a growing market for economical power stations, but this market is not currently well served. Those who have tried to serve this market have tended to not study to scope of the market, and thus have tried to serve this market with offerings that retailers and end users find lacking.
Having mentioned retailers for the first time, let us consider their concerns. When a retailer has an adult in a suite or any adolescent buy a set of jumper cables the retailer cringes. In exchange for a relatively small profit, the retailer is taking a serious risk of litigation. Does an adult man or woman in a suit know how to work with lead-acid technology? For that matter does an adult in overalls know this? Has an adolescent enough life experience that a personal injury jury would find it reasonable to sell them jumper cables? Is such a retailer now willing to also stock and sell economical power stations? Clearly, such power stations must be as inherently safe and intuitively usable as possible.
Current economical-grade power stations offerings are jumper cables, already discussed at length; trickle chargers; and secondary battery-in-a-boxes. A trickle charger, in this context, is an AC powered battery charger. Its portability is limited to the length of extension cords that one can use to connect it to an AC power source. In general, trickle chargers put out such a small current (a “trickle) that connecting them incorrectly is relatively safe and at most damages the application or the trickle charger itself.
In contrast, a secondary battery-in-a-box is kludge, usually a minimalist make do solution. A battery-in-a-box is distinguishable from a professional-grade stand alone power station, and from the about to be disclosed invention, in that these other solutions are optimized for suitability for their anticipated users and their particular end applications. As the label “battery-in-a-box” implies, this usually consists of a box, often an ice chest or a container that markedly resembles one; a battery, very often a standard automotive lead-acid battery; and a set of cable clamps.
The ice-chest rebalance of battery-in-a-box devices can perhaps be attributed to a desire to evoke similar convenience in the minds of potential buyers. This is unfortunate, since a potential buyers should instead be considering if the device has drainage, if sulfuric acid exits the power source, or ventilation if hydrogen gas exits the power source. Potential purchasers of a battery-in-a-box are frequently enticed by claims of high power output and fast recharge ability, with these claims achieved by not “going cheap” on the standard automotive lead-acid battery and the charger used. This exacerbates sulfuric acid and hydrogen gas risks. Bigger battery-in-a-box devices often have wheels in the same manner as larger ice chests. Where manufactures of battery-in-a-box devices do sometimes do go cheap is on cable clamps. Copper is relatively expensive, hence savings can be had by using less of it. This can be done by using smaller gage wire in cables, providing shorter cables, and using little copper and more plastic in clamps.
Typically, battery-in-a-box devices are only a high current or ampere-hours solution, but the present inventor has recently observed one exception. Recently a Chinese-manufactured battery-in-a-box device has appeared in some U.S. automotive accessory stores that includes a 120/240 VAC power inverter.